Hydrocarbon conversion with an acidic sulfur-free multimetallic catalytic composite

ABSTRACT

Hydrocarbons are converted by contacting them at hydrocarbon conversion conditions with an acidic sulfur-free multimetallic catalytic composite comprising a combination of catalytically effective amounts of a platinum group component, a rhenium component, a nickel component, and a halogen component with a porous carrier material. The platinum group component, rhenium component, nickel component, and halogen component are present in the multimetallic catalyst in amounts respectively, calculated on an elemental basis, corresponding to about 0.01 to about 2 wt. % platinum group metal, about 0.01 to about 2 wt. % rhenium, about 0.1 to about 5 wt. % nickel, and about 0.1 to about 3.5 wt. % halogen. Moreover, these metallic components are uniformly dispersed throughout the porous carrier material in carefully controlled oxidation states such that substantially all of the platinum group component is present therein in the elemental metallic state and substantially all of the nickel and rhenium components are present in the elemental metallic state or in a state which is reducible to the elemental metallic state under hydrocarbon conversion conditions or in a mixture of these states. A specific example of the type of hydrocarbon conversion process disclosed is a process for the catalytic reforming of a low-octane gasoline fraction wherein the gasoline fraction and a hydrogen stream are contacted with the acidic sulfur-free multimetallic catalyst disclosed herein at reforming conditions.

The subject of the present invention is a novel acidic sulfur-freemultimetallic catalytic composite which has exceptional activity andresistance to deactivation when employed in a hydrocarbon conversionprocess that requires a catalyst having both ahydrogenation-dehydrogenation function and a carbonium ion-formingfunction. More precisely, the present invention involves a noveldual-function acidic sulfur-free multimetallic catalytic compositewhich, quite surprisingly, enables substantial improvements inhydrocarbon conversion processes that have traditionally used adual-function catalyst. In another aspect, the present inventioncomprehends the improved processes that are produced by the use of anacidic sulfur-free catalytic composite comprising a combination ofcatalytically effective amounts of a platinum group component, a rheniumcomponent, a nickel component, and a halogen component with a porouscarrier material; specifically, an improved reforming process whichutilizes the subject catalyst to improve activity, selectivity, andstability characteristics.

Composites having a hydrogenation-dehydrogenation function and acarbonium ion-forming function are widely used today as catalysts inmany industries, such as the petroleum and petrochemical industry, toaccelerate a wide spectrum of hydrocarbon conversion reactions.Generally the carbonium ion-forming function is thought to be associatedwith an acid-acting material of the porous, adsorptive, refractory oxidetype which is typically utilized as the support or carrier for a heavymetal component such as the metals or compounds of metals of Groups Vthrough VIII of the Periodic Table to which are generally attributed thehydrogenation-dehydrogenation function.

These catalytic composites are used to accelerate a wide variety ofhydrocarbon conversion reactions such as hydrocracking, hydrogenolysis,isomerization, dehydrogenation, hydrogenation, desulfurization,cyclization, polymerization, alkylation, cracking, hydroisomerization,dealkylaation, transalkylation, etc. In many cases, the commericalapplications of these catalysts are in processes where more than one ofthe reactions are proceeding simultaneously. An example of this type ofprocess is reforming wherein a hydrocarbon feedstream containingparaffins and naphthenes is subjected to conditions which promotedehydrogenation of naphthenes to aromatics, dehydrocyclization ofparaffins to aromatics, isomerization of paraffins and naphthenes,hydrocracking and hydrogenolysis of napthenes and paraffins, and thelike reactions, to produce an octane-rich or aromatic-rich productstream. Another example is a hydrocracking process wherein catalysts ofthis type are utilized to effect selective hydrogenation and cracking ofhigh molecular weight unsaturated materials, selective hydrocracking ofhigh molecular weight materials, and other like reactions, to produce agenerally lower boiling, more valuable output stream. Yet anotherexample is a hydroisomerization process wherein a hydrocarbon fractionwhich is relatively rich in straight-chain paraffin compounds iscontacted with a dual-function catalyst to produce an output stream richin isoparaffin compounds.

Regardless of the reaction involved or the particular process involved,it is of critical importance that the dual-function catalyst exhibit notonly the capability to initially perform its specified functions, butalso that it has the capability to perform them satisfactorily forprolonged periods of time. The analytical terms used in the art tomeasure how well a particular catalyst performs its intended functionsin a particular hydrocarbon reaction environment are activity,selectivity, and stability. And for purposes of discussion here, theseterms are conveniently defined for a given charge stock as follows: (1)activity is a measure of the catalyst's ability to convert hydrocarbonreactants into products at a specified severity level where severitylevel means the conditions used--that is, the temperature, pressure,contact time, and presence of diluents such as H₂ ; (2) selectivityrefers to the amount of desired product or products obtained relative tothe amount or reactants charged or converted; (3) stability refers tothe rate of change with time of the activity and selectivityparameters--obviously, the smaller rate implying the more stablecatalyst. In a reforming process, for example, activity commonly refersto the amount of conversion that takes place for a given charge stock ata specified severity level and is typically measured by octane number ofthe C₅ + product stream; selectivity usually refers to the amount ofC₅ + yield and other valuable products, relative to the amount of thecharge, that is obtained at the particular activity or severity level;and stability is typically equated to the rate of change with time ofactivity, as measured by octane number of C₅ + product, and ofselectivity as measured by C₅ + yield. Actually, the last statement isnot strictly correct because generally a continuous reforming process isrun to produce a constant octane C₅ + product with severity level beingcontinuously adjusted to attain this result; and furthermore, theseverity level is for this process usually varied by adjusting theconversion temperature in the reaction zone so that, in point of fact,the rate of change of activity finds response in the rate of change ofconversion temperatures and changes in this parameter are customarilytaken as indicative of activity stability.

As is well known to those skilled in the art, the principal cause ofobserved deactivation or instability of a dual-function catalyst when itis used in a hydrocarbon conversion reaction is associated with the factthat coke forms on the surface of the catalyst during the course of thereaction. More specifically, in these hydrocarbon conversion processes,the conditions utilized typically result in the formation of heavy, highmolecular weight, black, solid or semi-solid, carbonaceous materialwhich is a hydrogen-deficient polymeric substance having properties akinto both polynuclear aromatics and graphite. This material coats thesurface of the catalyst and thus reduces its activity by shielding itsactive sites from the reactants. In other words, the performance of thisdual-function catalyst is sensitive to the presence of carbonaceousdeposits or coke on the surface of the catalyst. Accordingly, the majorproblem facing workers in this area of the art is the development ofmore active and/or selective catalytic composites that are not sosensitive to the presence of these carbonaceous materials and/or havethe capability to suppress the rate of the formation of thesecarbonaceous materials on the catalyst. Viewed in terms of performanceparameters, the problem is to develop a dual-function catalyst havingsuperior activity, selectivity, and stability characteristics. Inparticular, for a reforming process the problem is typically expressedin terms of shifting and stabilizing the C₅ + yield-octane relationshipat the lowest possible severity level--C₅ + yield being representativeof selectivity and octane being proportional to activity.

I have now found a dual-function acidic sulfur-free multimetalliccatalytic composite which possesses improved activity, selectivity, andstability characteristics when it is employed in a process for theconversion of hydrocarbons of the type which have heretofore utilizeddual-function acidic catalytic composites such as processes forisomerization, hydroisomerization, dehydrogenation, desulfurization,denitrogenization, hydrogenation, alkylation, dealkylation,disproportionation, polymerization, hydrodealkylation, transalkylation,cyclization, dehydrocyclization, cracking, hydrocracking, halogenation,reforming, demethanation, and the like processes. In particular, I haveascertained that an acidic sulfur-free catalyst, comprising acombination of catalytically effective amounts of a platinum groupcomponent, a rhenium component, a nickel component, and a halogencomponent with a porous refractory carrier material, can enable theperformance of hydrocarbon conversion processes utilizing dual-functioncatalysts to be substantially improved if the metallic components areuniformly dispersed throughout the carrier material and if theiroxidation states are controlled to be in the states hereinafterspecified. Moreover, I have determined that an acidic sulfur-freecatalytic composite comprising a combination of catalytically effectiveamounts of a platinum group component, a rhenium component, a nickelcomponent, and a chloride component with an alumina carrier material,can be utilized to substantially improve the performance of a reformingprocess which operates on a low-octane gasoline fraction to produce ahigh-octane reformate and a methane-rich gas stream if the metalliccomponents are uniformly dispersed throughout the alumina carriermaterial, and if the oxidation states of the metallic components arefixed in the state hereinafter specified. In the case of a reformingprocess, the principal advantage associated with the use of the presentinvention involves the acquisition of the capability to operate in astable manner in a high severity operation; for example, a low ormoderate pressure reforming process designed to produce a methane-richoff-gas stream and a C₅ + reformate having an octane of about 100 F-1clear. As indicated, the present invention essentially involves thefinding that the addition of a rhenium component and a nickel componentto a dual-function acidic hydrocarbon conversion catalyst containing aplatinum group component can enable the performance characteristics ofthe catalyst to be sharply and materially improved, if the hereinafterspecified limitations on amounts of ingredients, absence of sulfur,oxidation states of metals, and distribution of metallic components inthe support are met.

It is, accordingly, one object of the present invention to provide anacidic multimetallic hydrocarbon conversion catalyst having superiorperformance characteristics when utilized in a hydrocarbon conversionprocess. A second object is to provide an acidic sulfur-freemultimetallic catalyst having dual-function hydrocarbon conversionperformance characteristics that are relatively insensitive to thedeposition of hydrocarbonaceous material thereon. A third object is toprovide preferred method of preparation of this acidic sulfur-freemultimetallic catalytic composite which insures the achievement andmaintenance of its properties. Another object is to provide an improvedreforming catalyst having superior activity, selectivity, and stabilitycharacteristics. Yet another object is to provide a dual-functionhydrocarbon conversion catalyst which utilizes a combination of arhenium component and a nickel component to beneficially interact withand promote and acidic sulfur-free catalyst containing a platinum groupcomponent.

In brief summary, the present invention is, in one embodiment, an acidicsulfur-free catalytic composite comprising a porous carrier materialcontaining, on an elemental basis, about 0.01 to about 2 wt. % platinumgroup metal, about 0.01 to about 2 wt. % rhenium, about 0.1 to about 5wt. % nickel, and about 0.1 to about 3.5 wt. % halogen, wherein theplatinum group metal, rhenium, and nickel are uniformly dispersedthroughout the porous carrier material, wherein substantially all of theplatinum group metal is present in the elemental metallic state, andwherein substantially all of the nickel and rhenium are present in theelemental metallic state or in a state which is reducible to theelemental metallic state under hydrocarbon conversion conditions or in amixture of these states.

A second embodiment relates to an acidic sulfur-free catalytic compositecomprising a porous carrier material containing, on an elemental basis,about 0.05 to about 1 wt. % platinum group metal, about 0.05 to about 1wt. % rhenium, about 0.25 to about 2.5 wt. % nickel, and about 0.05 toabout 1.5 wt. % halogen, wherein the platinum group metal, rhenium andnickel are uniformly dispersed throughout the porous carrier material,wherein substantially all of the platinum group metal is present in thecorresponding elemental metallic state, and wherein substantially all ofthe nickel and rhenium are present in the elemental metallic state or ina state which is reducible to the elemental metallic state underhydrocarbon conversion conditions or in a mixture of these states.

A third embodiment relates to the catalytic composite described in thefirst or second embodiment wherein the halogen is combined chloride.

Yet another embodiment involves a process for the conversion of ahydrocarbon comprising contacting the hydrocarbon and hydrogen with thecatalytic composite described above in the first or second or thirdembodiment at hydrocarbon conversion conditions.

A preferred embodiment comprehends a process for reforming a gasolinefraction which comprises contacting the gasoline fraction and hydrogenwith the catalytic composite described above in the first or second orthird embodiment at reforming conditions selected to produce a highoctane reformate and a methane-rich gas stream.

A highly preferred embodiment is a process for reforming a gasolinefraction which comprises contacting the gasoline fraction and hydrogenin a substantially water-free and sulfur-free environment with thecatalytic composite characterized in the first, second, or thirdembodiment at reforming conditions selected to produce a high octanereformate and a methane-rich gas stream.

Other objects and embodiments of the present invention relate toadditional details regarding preferred catalytic ingredients, preferredamounts of ingredients, suitable methods of composite preparation,operating conditions for use in the hydrocarbon conversion processes,and the like particulars, which are hereinafter given in the followingdetailed discussion of each of these facets of the present invention.

The acidic sulfur-free multimetallic catalyst of the present inventioncomprises a porous carrier material or support having combined therewithcatalytically effective amounts of a platinum group component, a rheniumcomponent, a nickel component, and a halogen component.

Considering first the porous carrier material utilized in the presentinvention, it is preferred that the material be a porous, adsorptive,high-surface area support having a surface area of about 25 to about 500m² /g. The porous carrier material should be relatively refractory tothe conditions utilized in the hydrocarbon conversion process, and it isintended to include within the scope of the present invention carriermaterials which have traditionally been utilized in dual-functionhydrocarbon conversion catalysts such as: (1) activated carbon, coke, orcharcoal; (2) silica or silica gel, silicon carbide, clays, andsilicates including those synthetically prepared and naturallyoccurring, which may or may not be acid treated, for example, attapulgusclay, china clay, diatomaceous earth, fuller's earth, kaolin,kieselguhr, etc., (3) ceramics, porcelain, crushed firebrick, bauxite;(4) refractory inorganic oxides such as alumina, titanium dioxide,zirconium dioxide, chromium oxide, beryllium oxide, vanadium oxide,cesium oxide, hafnium oxide, zinc oxide, magnesia, boria, thoria,silica-alumina, silica-magnesia, chromia-alumina, alumina-boria,silica-zirconia, etc.; (5) crystalline zeolitic aluminosilicates such asnaturally occurring or synthetically prepared mordenite and/orfaujasite, either in the hydrogen form or in a form which has beentreated with multivalent cations; (6) spinels such as MgAl₂ O₄, FeAl₂O₄, ZnAl₂ O₄, MnAl₂ O₄, CaAl₂ O₄, and other like compounds having theformula MO.sup.. Al₂ O₃ where M is a metal having a valence of 2; and,(7) combinations of elements from one or more of these groups. Thepreferred porous carrier materials for use in the present invention arerefractory inorganic oxides, with best results obtained with an aluminacarrier material. Suitable alumina materials are the crystallinealuminas known as gamma-, eta-, and theta-alumina, with gamma- oreta-alumina giving best results. In addition, in some embodiments thealumina carrier material may contain minor proportions of other wellknown refractory inorganic oxides such as silica, zirconia, magnesia,etc.; however, the preferred support is substantially pure gamma- oreta-alumina. Preferred carrier materials have an apparent bulk densityof about 0.3 to about 0.8 g/cc and surface area characteristics suchthat the average pore diameter is about 20 to 300 Angstroms, the porevolume is about 0.1 to about 1 cc/g and the surface area is about 100 toabout 500 m² /g. In general, best results are typically obtained with agamma-alumina carrier material which is used in the form of sphericalparticles having: a relatively small diameter (i.e. typically about 1/16inch), an apparent bulk density of about 0.3 to about 0.8 g/cc, a porevolume of about 0.4 ml/g, and a surface area of about 200 m² /g.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or natural occurring. Whatevertype of alumina is employed, it may be activated prior to use by one ormore treatments including drying, calcination, steaming, etc., and itmay be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide, to a salt of aluminum such as aluminum chloride,aluminum nitrate etc., in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina. The aluminacarrier may be formed in any desired shape such as spheres, pills,cakes, extrudates, powders, granules, tablets, etc., and utilized in anydesired size. For the purpose of the present invention a particularlypreferred form of alumina is the sphere; and alumina spheres may becontinuously manufactured by the well known oil drop method whichcomprises: forming an alumina hydrosol by any of the techniques taughtin the art and preferably by reacting aluminum metal with hydrochloricacid, combining the resultant hydrosol with a suitable gelling agent anddropping the resultant mixture into an oil bath maintained at elevatedtemperatures. The droplets of the mixture remain in the oil bath untilthey set and form hydrogel spheres. The spheres are then continuouslywithdrawn from the oil bath and typically subjected to specific agingtreatments in oil and an ammoniacal solution to further improve theirphysical characteristics. The resulting aged and gelled particles arethen washed and dried at a relatively low temperature of about 300° F.to about 400° F. and subjected to a calcination procedure at atemperature of about 850° F. to about 1300° F. for a period of about 1to about 20 hours. This treatment effects conversion of the aluminahydrogel to the corresponding crystalline gamma-alumina. See theteachings of U.S. Pat. No. 2,620,314 for additional details.

One essential ingredient of the subject catalyst is the platinum groupcomponent. That is, it is intended to cover the use of platinum,iridium, osmium, ruthenium, rhodium, palladium, or mixtures thereof as acomponent of the present composite. It is an essential feature of thepresent invention that substantially all of this platiuum groupcomponent exists within the final catalytic composite in the elementalmetallic state. Generally, the amount of this component present in thefinal catalytic composite is small compared to the quantities of theother components combined therewith. In fact, the platinum groupcomponent generally will comprise about 0.01 to about 2 wt. % of thefinal catalytic composite, calculated on an elemental basis. Excellentresults are obtained when the catalyst contains about 0.05 to about 1wt. % of platinum, iridium, rhodium, or palladium metal. Particularlypreferred mixtures of these metals are platinum and iridium and platinumand rhodium.

This platinum group component may be incorporated in the catalyticcomposite in any suitable manner known to result in a relatively uniformdistribution of this component in the carrier material such ascoprecipitation or cogellation, ion exchange, or impregnation. Thepreferred method of preparing the catalyst involves the utilization of asoluble, decomposable compound of platinum group metal to impregnate thecarrier material in a relatively uniform manner. For example, thiscomponent may be added to the support by commingling the latter with anaqueous solution of chloroplatinic or chloroiridic or chloropalladicacid. Other water-soluble compounds or complexes of platinum groupmetals may be employed in impregnation solutions and include ammoniumchloroplatinate, bromoplatinic acid, platinum trichloride, platinumtetrachloride hydrate, platinum dichlorocarbonyl dichloride,dinitrodiaminoplatinum, sodium tetranitroplatinate (II), palladiumchloride, palladium nitrate, palladium sulfate, diamminepalladium (II)hydroxide, tetramminepalladium (II) chloride, hexamminerhodium chloride,rhodium carbonylchloride, rhodium trichloride, hydrate, rhodium nitrate,sodium hexachlororhodate (III), sodium hexanitrorhodate (III), iridiumtribromide, iridium dichloride, iridium tetrachloride, sodiumhexanitroiridate (III), potassium or sodium chloroiridate, potassiumrhodium oxalate, etc. The utilization of a platinum, iridium, rhodium,or palladium chloride compound, such as chloroplatinic, chloroiridic orchloropalladic acid or rhodium trichloride hydrate, is preferred sinceit facilitates the incorporation of both the platinum group componentand at least a minor quantity of the halogen component in a single step.Hydrogen chloride or the like acid is also generally added to theimpregnation solution in order to further facilitate the incorporationof the halogen component and the uniform distribution of the metalliccomponents throughout the carrier material. In addition, it is generallypreferred to impregnate the carrier material after it has been calcinedin order to minimize the risk of washing away the valuable platinum orpalladium compounds; however, in some cases it may be advantageous toimpregnate the carrier material when it is in a gelled state.

A second essential ingredient of the present catalytic composite is arhenium component. It is of fundamental importance that substantiallyall of the rhenium component exists within the catalytic composite ofthe present invention in the elemental metallic state or in a statewhich is reducible to the elemental metallic state under hydrocarbonconversion conditions or in a mixture of these states. The rheniumcomponent may be utilized in the composite in any amount which iscatalytically effective, with the preferred amount being about 0.01 toabout 2 wt. % thereof, calculated on an elemental basis. Typically, bestresults are obtained with about 0.05 to about 1 wt. % rhenium. It isadditionally preferred to select the specified amount of rhenium fromwithin this broad weight range as a function of the amount of theplatinum group component, on an atomic basis, as is explainedhereinafter.

This rhenium component may be incorporated into the catalytic compositein any suitable manner known to those skilled in the catalystformulation art which results in a relatively uniform distribution ofrhenium in the carrier material such as by coprecipitation,ion-exchange, or impregnation. In addition, it may be added at any stageof the preparation of the composite--either during preparation of thecarrier material of thereafter--and the precise method of incorporationused is not deemed to be critical. However, best results are obtainedwhen the rhenium component is relatively uniformly distributedthroughout the carrier material in a relatively small particle size, andthe preferred procedures are the ones known to result in a compositehaving this relatively uniform distribution. One acceptable procedurefor incorporating this component into the composite involves cogellingor coprecipitating the rhenium component during the preparation of thepreferred carrier material, alumina. This procedure usually comprehendsthe addition of a soluble, decomposable compound of rhenium such asperrhenic acid or a salt thereof to the alumina hydrosol before it isgelled. The resulting mixture is then finished by conventional gelling,aging, drying, and calcination steps are explained hereinbefore. Apreferred way of incorporating this component is an impregnation stepwherein the porous carrier material is impregnated with a suitablerhenium-containing solution either before, during, or after the carriermaterial is calcined. Preferred impregnation solutions are aqueoussolutions of water soluble, decomposable rhenium compounds such asammonium perrhenate, sodium perrhenate, potassium perrhenate, potassiumrhenium oxychloride (K₂ ReOCl₅), potassium hexachlororhenate (IV),rhenium chloride, rhenium heptoxide, and the like compounds. Bestresults are ordinarily obtained when the impregnation solution is anaqueous solution of perrhenic acid. This component can be added to thecarrier material either prior to, simultaneously with, or after theother metallic components are combined therewith. Best results areusually achieved when this component is added simultaneously with theother metallic components. In fact, excellent results are obtained witha one step impregnation procedure using an acidic sulfur-free aqueoussolution containing chloroplatinic acid, perrhenic acid, nickelchloride, and hydrochloric acid.

A third essential ingredient of the acidic sulfur-free multi-metalliccatalytic composite of the present invention is a nickel component.Although this component may be initially incorporated into the compositein many different decomposable forms which are hereinafter stated, mybasic finding is that the catalytically active state for hydrocarbonconversion with this component is the elemental metallic state.Consequently, it is a feature of my invention that substantially all ofthe nickel component exists in the catalytic composite either in theelemental metallic state or in a state which is reducible to theelemental state under hydrocarbon conversion conditions or in a mixtureof these states. Examples of this reducible state are obtained when thenickel component is initially present in the form of nickel oxide,halide, hydroxide, oxyhalide, and the like reducible compounds. As acorollary to this basic finding on the active state of the nickelcomponent, it follows that the presence of nickel in forms which are notreducible at hydrocarbon conversion conditions is to be scrupulouslyavoided if the full benefits of the present invention are to berealized. Illustrative of these undesired forms are nickel sulfide andthe nickel oxysulfur compounds such as nickel sulfate. Best results areobtained when the composite initially contains all of the nickelcomponent in the elemental metallic state or in a reducible oxide stateor in a mixture of these states. All available evidence indicates thatthe preferred preparation procedure specifically described in Example Iresults in a catalyst having the nickel component in the elementalmetallic state or in a reducible oxide form. The nickel component may beutilized in the composite in any amount which is catalyticallyeffective, with the preferred amount being about 0.1 to about 5 wt. %thereof, calculated on an elemental nickel basis. Typically, bestresults are obtained with about 0.25 to about 2.5 wt. % nickel. It is,additionally, preferred to select the specific amount of nickel fromwithin this broad weight range as a function of the amount of theplatinum group component, on an atomic basis, as is explainedhereinafter.

The nickel component may be incorporated into the catalytic composite inany suitable manner known to those skilled in the catalyst formulationart to result in a relatively uniform distribution of nickel in thecarrier material such as coprecipitation, cogellation, ion exchange,impregnation, etc. In addition, it may be added at any stage of thepreparation of the composite--either during preparation of the carriermaterial or thereafter--since the precise method of incorporation usedis not deemed to be critical. However, best results are obtained whenthe nickel component is relatively uniformly distributed throughout thecarrier material in a relatively small particle or cyrstallite size, andthe preferred procedures are the ones that are known to result in acomposite having a relatively uniform distribution of the nickel moietyin a relatively small particle size. One acceptable procedure forincorporating this component into the composite involves cogelling orcoprecipitating the nickel component during the preparation of thepreferred carrier material, alumina. This procedure usually comprehendsthe addition of a soluble, decomposable, and reducible compound ofnickel such as nickel chloride or nitrate to the alumina hydrosol beforeit is gelled. The resulting mixture is then finished by conventionalgelling, aging, drying, and calcination steps as explained hereinbefore.One preferred way of incorporating this component is an impregnationstep wherein the porous carrier material is impregnated with a suitablenickel-containing solution either before, during, or after the carriermaterial is calcined or oxidized. The solvent used to form theimpregnation solution may be water, alcohol, ether, or any othersuitable organic or inorganic solvent provided the solvent does notadversely interact with any of the other ingredients of the composite orintefere with the distribution and reduction of the nickel component.Preferred impregnation solutions are equeous solutions of water-soluble,decomposable, and reducible nickel compounds or complexes such as nickelbromate, nickel bromide, nickel perchlorate, nickel chloride, nickelfluoride, nickel iodide, nickel nitrate, hexamminenickel (II) chloride,diaquotetramminenickel (II) nitrate, hexamminenickel (II) nitrate, andthe like compounds or complexes. Best results are ordinarily obtainedwhen the impregnation solution is an aqueous acidic solution of nickelchloride or nickel nitrate. This nickel component can be added to thecarrier material, either prior to, simultaneously with, or after theother metallic components are combined therewith. Best results areusually achieved when this component is added simultaneously with theplatinum group and rhenium components via an acidic aqueous impregnationsolution. In fact, excellent results are obtained, as reported in theexamples, with an impregnation procedure using an acidic aqueoussolution comprising chloroplatinic acid, nickel chloride, perrhenicacid, and hydrochloric acid.

It is essential to incorporate a halogen component into the acidicsulfur-free multimetallic catalytic composite of the present invention.Although the precise form of the chemistry of the association of thehalogen component with the carrier material is not entirely known, it iscustomary in the art to refer to the halogen component as being combinedwith the carrier material, or with the other ingredients of the catalystin the form of the halide (e.g. as the chloride). This combined halogenmay be either fluorine, chlorine, iodine, bromine, or mixtures thereof.Of these, fluorine and, particularly, chlorine are preferred for thepurposes of the present invention. The halogen may be added to thecarrier material in any suitable manner, either during preparation ofthe support or before or after the addition of the other components. Forexample, the halogen may be added, at any stage of the preparation ofthe carrier material or to the calcined carrier material, as an aqueoussolution of a suitable, decomposable halogen-containing compound such ashydrogen fluoride, hydrogen chloride, hydrogen bromide, ammoniumchloride, etc. The halogen component or a portion thereof, may becombined with the carrier material during the impregnation of the latterwith the platinum group, rhenium, or nickel components; for example,through the utilization of a mixture of chloroplatinic acid and hydrogenchloride. In another situation, the alumina hydrosol which is typicallyutilized to form the preferred alumina carrier material may containhalogen and thus contribute at least a portion of the halogen componentto the final composite. For reforming, the halogen will be typicallycombined with the carrier material in an amount sufficient to result ina final composite that contains about 0.1 to about 3.5%, and preferablyabout 0.5 to about 1.5%, by weight, of halogen, calculated on anelemental basis. In isomerization or hydrocracking embodiments, it isgenerally preferred to utilize relatively larger amounts of halogen inthe catalyst--typically ranging up to about 10 wt. % halogen calculatedon an elemental basis, and more preferably, about 1 to about 5 wt. %. Itis to be understood that the specified level of halogen component in theinstant catalyst can be achieved or maintained during use in theconversion of hydrocarbons by continuously or periodically adding to thereaction zone a decomposable halogen-containing compound such as anorganic chloride (e.g. ethylene dichloride, carbon tetrachloride,t-butyl chloride) in an amount of about 1 to 100 wt. ppm. of thehydrocarbon feed, and preferably about 1 to 10 wt. ppm.

Regarding especially preferred amounts of the various metalliccomponents of the subject catalyst, I have found it to be a goodpractice to specify the amounts of the rhenium component and the nickelcomponent as a function of the amount of the platinum group component.On this basis, the amount of the rhenium component is ordinarilyselected so that the atomic ratio of rhenium to platinum group metalcontained in the composite is about 0.05:1 to about 10:1, with thepreferred range being about 0.2:1 to about 5:1. Similarly, the amount ofthe nickel component is ordinarily selected to produce a compositecontaining an atomic ratio of nickel to platinum group metal of about0.2:1 to about 66:1, with the preferred range being about 0.8:1 to about18:1.

Another significant parameter for the instant catalyst is the "totalmetals content" which is defined to be the sum of the platinum groupcomponent, the rhenium component, and the nickel component, calculatedon an elemental basis. Good results are ordinarily obtained with thesubject catalyst when this parameter is fixed at a value of about 0.15to about 4 wt. %, with best results ordinarily achieved at a metalsloading of about 0.3 to about 3 wt. %.

In embodiments of the present invention wherein the instantmultimetallic catalytic composite is used for the dehydrogenation ofdehydrogenatable hydrocarbons or for the hydrogenation of hydrogenatablehydrocarbons, it is ordinarily a preferred practice to include an alkalior alkaline earth metal component in the composite and to minimize oreliminate the hydrogen component. More precisely, this optionalingredient is selected from the group consisting of the compounds of thealkali metals--cesium, rubidium, potassium, sodium, and lithium--and thelike compounds of the alkaline earth metals--calcium, strontium, barium,and magnesium. Generally, good results are obtained in these embodimentswhen this component consitutes about 0.1 to about 5 wt. % of thecomposite, calculated on an elemental basis. This optional alkali oralkaline earth metal component can be incorporated in the composite inany of the known ways, with impregnation with an aqueous solution of asuitable water-soluble, decomposable compound being preferred.

An optional ingredient for the multimetallic catalyst of the presentinvention is a Friedel-Crafts metal halide component. This ingredient isparticularly useful in hydrocarbon conversion embodiments of the presentinvention wherein it is preferred that the catalyst utilized has astrong acid or cracking function associated therewith--for example, anembodiment wherein hydrocarbons are to be hydrocracked or isomerizedwith the catalyst of the present invention. Suitable metal halides ofthe Friedel-Crafts type include aluminum chloride, aluminum bromide,ferric chloride, ferric bromide, zinc chloride, and the like compounds,with the aluminum halides and, particularly aluminum chloride,ordinarily yielding best results. Generally, this optional ingredientcan be incorporated into the composite of the present invention by anyof the conventional methods for adding metallic halides of this type;however, best results are ordinarily obtained when the metallic halideis sublimed onto the surface of the carrier material according to thepreferred method disclosed in U.S. Pat. No. 2,999,074. The component cangenerally be utilized in any amount which is catalytically effective,with a value selected from the range of about 1 to about 100 wt. % ofthe carrier material generally being preferred.

Regardless of the details of how the components of the catalyst arecombined with the porous carrier material, the final catalyst generallywill be dried at a temperature of about 200° to about 600° F. for aperiod of at least about 2 to about 24 hours or more, and finallycalcined or oxidized at a temperature of about 700° F. to about 1100° F.in a sulfur-free air or oxygen atmosphere for a period of about 0.5 toabout 10 hours in order to convert substantially all of the metalliccomponents to the corresponding reducible oxide forms. Because a halogencomponent is utilized in the catalyst, best results are generallyobtained when the halogen content of the catalyst is adjusted during theoxidation step by including a halogen or a halogen-containing compoundsuch as HCl in the air or oxygen atmosphere utilized. In particular,when the halogen component of the catalyst is chlorine, it is preferredto use a mole ratio of H₂ O to HCl of about 5:1 to about 100:1 during atleast a portion of the oxidation step in order to adjust the finalchlorine content of the catalyst to a range of about 0.1 to about 3.5wt. %. Preferably, the duration of this halogenation step is about 1 to5 hours.

The resultant oxidized catalytic composite is preferably subjected to asubstantially water-free, sulfur-free, and hydrocarbon-free reductionstep prior to its use in the conversion of hydrocarbons. This step isdesigned to selectively reduce substantially all of the platinum groupcomponent to the elemental metallic state and to insure a uniform andfinely divided dispersion of the metallic components throughout thecarrier material. Preferably substantially pure sulfur-free and dryhydrogen (i.e. less than 20 vol. ppm. H₂ O) is used as the reducingagent in this step. The reducing agent is contacted with the oxidizedcatalyst at conditions including a reduction temperature of about 800°F. to about 1200° F. and a period of time of about 0.5 to 10 hourseffective to reduce substantially all of the platinum group component tothe elemental metallic state. This reduction treatment may be performedin situ as part of a start-up sequence if precautions are taken topredry the plant to a substantially water-free state and ifsubstantially water-free and hydrocarbon-free hydrogen is used.

The resulting reduced catalytic composite is, in accordance with thebasic concept of the present invention, preferably maintained in asulfur-free state both during its preparation and thereafter during itsuse in the conversion of hydrocarbons. As indicated previously, thebeneficial interaction of the nickel component with the otheringredients of the present catalytic composite is contingent upon themaintenance of the nickel moiety in a highly dispersed, readilyreducible state in the carrier material. Sulfur in the form of sulfideadversely interferes with both the dispersion and reducibility of thenickel component and consequently it is a highly preferred practice toavoid presulfiding the reduced acidic multimetallic catalyst from thereduction step. Once the catalyst has been exposed to hydrocarbon for asufficient period of time to lay down a protective layer of carbon orcoke on the surface thereof, the sulfur sensitivity of the resultingcarbon-containing composite changes rather markedly and the presence ofsmall amounts of sulfur can be tolerated without permanently disablingthe catalyst. The exposure of the freshly reduced catalyst to sulfur canseriously damage the nickel component thereof and consequentlyjeopardize the superior performance characteristics associatedtherewith. However, once a protective layer of carbon is established onthe catalyst the sulfur deactivation effect is less permanent and sulfurcan be purged therefrom by exposure to a sulfur-free hydrogen stream ata temperature of about 800° to 1100° F.

According to the present invention, a hydrocarbon charge stock andhydrogen are contacted with the instant acidic sulfur-free multimetalliccatalyst in a hydrocarbon conversion zone. This contacting may beaccomplished by using the catalyst in a fixed bed system, a moving bedsystem, a fluidized bed system, or in a batch type operation; however,in view of the danger of attrition losses of the valuable catalyst andof well known operational advantages, it is preferred to use either afixed bed system or a dense-phase moving bed system such as is shown inU.S. Pat. No. 3,725,249. It is also contemplated that this contactingstep can be performed in the presence of a physical mixture of particlesof the catalyst of the present invention and particles of a conventionaldual-function catalyst of the prior art. In a fixed bed system, ahydrogen-rich gas and the charge stock are preheated by any suitableheating means to the desired reaction temperature and then passed into aconversion zone containing a fixed bed of the acidic sulfur-freemultimetallic catalyst. It is, of course, understood that the conversionzone may be one or more separate reators with suitable meanstherebetween to insure that the desired conversion temperature ismaintained at the entrance to each reactor. It is also important to notethat the reactants may be contacted with the catalyst bed in eitherupward, downward, or radial flow fashion with the latter beingpreferred. In addition, the reactants may be in the liquid phase, amixed liquid-vapor phase, or a vapor phase when they contact thecatalyst, with best results obtained in the vapor phase.

In the case where the acidic sulfur-free multimetallic catalyst of thepresent invention is used in a reforming operation, the reforming systemwill typically comprise a reforming zone containing one or more fixedbeds or dense-phase moving beds of the catalyst. In a multiple bedsystem, it is of course within the scope of the present invention to usethe present catalyst in less than all of the beds with a conventionaldualfunction catalyst being used in the remainder. This reforming zonemay be one or more separate reactors with suitable heating meanstherebetween to compensate for the endothermic nature of the reactionsthat take place in each catalyst bed. The hydrocarbon feed stream thatis charged to this reforming system will comprise hydrocarbon fractionscontaining naphthenes and paraffins that boil within the gasoline range.The preferred charge stocks are those consisting essentially ofnaphthenes and paraffins, although in some cases aromatics and/orolefins may also be present. This preferred class includes straight rungasolines, natural gasolines, synthetic gasolines, partially reformedgasolines, and the like. On the other hand, it is frequentlyadvantageous to charge thermally or catalytically cracked gasolines orhigher boiling fractions thereof. Mixtures of straight run and crackedgasolines can also be used to advantage. The gasoline charge stock maybe a full boiling gasoline having an initial boiling point of from about50° to about 150° F. and an end boiling point within the range of fromabout 325° to about 425° F., or may be a selected fraction thereof whichgenerally will be a higher boiling fraction commonly referred to as aheavy naptha--for example, a naphtha boiling in the range of C₇ to 400°F. In some cases, it is also advantageous to charge pure hydrocarbons ormixtures of hydrocarbons that have been extracted from hydrocarbondistillates--for example, straight-chain paraffins--which are to beconverted to aromatics. It is preferred that these charge stocks betreated by conventional catalytic pretreatment methods such ashydrorefining, hydrotreating, hydrodesulfurization, etc., to removesubstantially all sulfurous, nitrogenous, and water-yieldingcontaminants therefrom and to saturate any olefins that may be containedtherein.

In other hydrocarbon conversion embodiments, the charge stock will be ofthe conventional type customarily used for the particular kind ofhydrocarbon conversion being effected. For example, in a typicalisomerization embodiment the charge stock can be a paraffinic stock richin C₄ to C₈ normal paraffins, or a normal butane-rich stock, or an-hexanerich stock, or a mixture of xylene isomers, etc. In adehydrogenation embodiment, the charge stock can be any of the knowndehydrogenatable hydrocarbons such as an aliphatic compound containing 2to 30 carbon atoms per molecule, a C₄ to C₃₀ normal paraffin, a C₈ toC₁₂ alkylaromatic, a naphthene, and the like. In hydrocrackingembodiments, the charge stock will be typically a gas oil, heavy crackedcycle oil, etc. In addition, alkylaromatic and naphthenes can beconveniently isomerized by using the catalyst of the present invention.Likewise, pure hydrocarbons or substantially pure hydrocarbons can beconverted to more valuable products by using the acidic sulfur-freemultimetallic catalyst of the present invention in any of thehydrocarbon conversion processes, known to the art, that use adual-function catalyst.

Since sulfur has a high affinity for nickel at hydrocarbon conversionconditions, best results are achieved in the conversion of hydrocarbonswith the instant acidic sulfur-free multimetallic catalytic compositewhen the catalyst is used in a substantially sulfur-free environment.This is particularly true in the catalytic reforming embodiment of thepresent invention. The expression "substantially sulfur-freeenvironment" is intended to mean that the total amount (expressed asequivalent elemental sulfur) of sulfur of sulfur-containing compounds,which are capable of producing a metallic sulfide at the reactionconditions used, entering the reaction zone containing the instantcatalyst from any source is continuously maintained at an amountequivalent to less than 10 wt. ppm of the hydrocarbon charge stock, morepreferably less than 5 wt. ppm., and most preferably less than 1 wt.ppm. Since in the ordinary operation of a conventional catalyticreforming process, wherein influent hydrogen is autogenously produced,the prime source for any sulfur entering the reforming zone is thehydrocarbon charge stock, maintaining the charge stock substantiallyfree of sulfur is ordinarily sufficient to ensure that the environmentcontaining the catalyst is maintained in the substantially sulfur-freestate. More specifically, since hydrogen is a by-product of thecatalytic reforming process, ordinarily the input hydrogen streamrequired for the process is obtained by recycling a portion of thehydrogen-rich stream recovered from the effluent withdrawn from thereforming zone. In this typical situation, this recycle hydrogen streamwill ordinarily be substantially free of sulfur if the charge stock ismaintained free of sulfur. If autogenous hydrogen is not utilized, thenof course the concept of the present invention requires that the inputhydrogen stream be maintained substantially sulfur-free; that is, lessthan 10 vol. ppm of H₂ S, preferably less than 5 vol. ppm, and mostpreferably less than 1 vol ppm.

The only other possible sources of sulfur that could interfere with theperformance of the instant catalyst are sulfur that is initiallycombined with the catalyst and/or with the plant hardware. As indicatedhereinbefore, a feature of the present acidic multimetallic catalyst isthat it is maintained substantially sulfur-free; therefore, sulfurreleased from the catalyst is not usually a problem in the presentprocess. Hardware sulfur is ordinarily not present in a new plant; itonly becomes a problem when the present processs is to be implemented ina plant that has seen service with a sulfur-containing feed-stream. Inthis latter case, the preferred practice of the present inventioninvolves an initial pretreatment of the sulfur-containing plant in orderto remove substantially all of the decomposable hardware sulfurtherefrom. This can be easily accomplished by any of the techniques forstripping sulfur from hardware known to those in the art; for example,by the circulation of a substantially sulfur-free hydrogen streamthrough the internals of the plant at a relatively high temperature ofabout 800° to about 1200° F. until the H₂ S content of the effluent gasstream drops to a relatively low level--typically, less than 5 vol. ppmand preferably less than 2 vol. ppm. In sum, the preferred sulfur-freefeature of the present invention requires that the total amount ofdetrimental sulfur entering the hydrocarbon conversion zone containingthe hereinbefore described acidic sulfur-free multimetallic catalystmust be continuously maintained at a substantially low level;specifically, the amount of sulfur must be held to a level equivalent toless than 10 wt. ppm., and preferably less than 1 wt. ppm., of the feed.

In the case where the sulfur content of the feed stream for the presentprocess is greater than the amounts previously specified, it is, ofcourse, necessary to treat the charge stock in order to remove theundesired sulfur contaminants therefrom. This is easily accomplished byusing any one of the conventional catalytic pretreatment methods such ashydrorefining, hydrotreating, hydrodesulfurization, and the like toremove substantially all sulfurous, nitrogenous, and water-yieldingcontaminants from this feed stream. Ordinarily, this involves subjectingthe sulfur-containing feedstream to contact with a suitablesulfur-resistant hydrorefining catalyst in the presence of hydrogenunder conversion conditions selected to decompose sulfur contaminantscontained therein and form hydrogen sulfide. The hydrorefining catalysttypically comprises one or more of the oxides or sulfides of thetransition metals of Groups VI and VIII of the Periodic Table. Aparticularly preferred hydrorefining catalyst comprises a combination ofa metallic component from the iron group metals of Group VIII and of ametallic component of the Group VI transition metals combined with asuitable porous refractory support. Particularly good results have beenobtained when the iron group component is cobalt and/or nickel and theGroup VI transition metal is molybdenum or tungsten. The preferredsupport for this type of catalyst is a refractory inorganic oxide of thetype previously mentioned. For example, good results are obtained with ahydrorefining catalyst comprising cobalt oxide and molybdenum oxidesupported on a carrier material comprising alumina and silica. Theconditions utilized in this hydrorefining step are ordinarily selectedfrom the following ranges: a temperature of about 600° to about 950° F.,a pressure of about 500 to about 5000 psig., a liquid hourly spacevelocity of about 1 to about 20 hr.⁻ ¹, and a hydrogen circulation rateof about 500 to about 10,000 standard cubic feet of hydrogen per barrelof charge. After this hydrorefining step, the hydrogen sulfide, ammonia,and water liberated therin, are then easily removed from the resultingpurified charge stock by conventional means such as a suitable strippingoperation. Specific hydrorefining conditions are selected from theranges given above as a function of the amounts of kinds of the sulfurcontaminants in the feedstream in order to produce a substantiallysulfur-free charge stock which is then charged to the process of thepresent invention.

In a reforming embodiment, it is generally preferred to utilize thenovel acidic sulfur-free multimetallic catalytic composite in asubstantially water-free environment. Essential to the achievement ofthis condition in the reforming zone is the control of the water levelpresent in the charge stock and the hydrogen stream which is beingcharged to the zone. Best results are ordinarily obtained when the totalamount of water entering the conversion zone from any source is held toa level less than 20 ppm. and preferably less than 5 ppm. expressed asweight of equivalent water in the charge stock. In general, this can beaccomplished by careful control of the water present in the charge stockand in the hydrogen stream. The charge stock can be dried by using anysuitable drying means known to the art, such as a conventional solidadsorbent having a high selectivity for water, for instance, sodium orcalcium crystalline aluminosilicates, silica gel, activated alumina,molecular sieves, anhydrous calcium sulfate, high surface area sodium,and the like adsorbents. Similarly, the water content of the chargestock may be adjusted by suitable stripping operations in afractionation column or like device. And in some cases, a combination ofadsorbent drying and distillation drying may be used advantageously toeffect almost complete removal of water from the charge stock. In anespecially preferred mode of operation, the charge stock is dried to alevel corresponding to less than 5 wt. ppm. of H₂ O equivalent. Ingeneral, it is preferred to maintain the hydrogen stream entering thehydrocarbon conversion zone at a level of about 10 vol. ppm. of water orless and most preferably about 5 vol. ppm. or less. If the water levelin the hydrogen stream is too high, drying of same can be convenientlyaccomplished by contacting the hydrogen stream with a suitable desiccantsuch as those mentioned above.

In the reforming embodiment, an effluent stream is withdrawn from thereforming zone and passed through a cooling means to a separation zone,typically maintained at about 25° to 150° F., wherein a hydrogen-richgas stream is separated from a high octane liquid product stream,commonly called an unstabilized reformate. When the water level in thehydrogen stream is outside the range previously specified, at least aportion of this hydrogen-rich gas stream is withdrawn from theseparating zone and passed through an adsorption zone containing anadsorbent selective for water. The resultant substantially water-freehydrogen stream can then be recycled through suitable compressing meansback to the reforming zone. The liquid phase from the separating zone istypically withdrawn and commonly treated in a fractionating system inorder to adjust the butane concentration, thereby controlling front-endvolatility of the resulting reformate.

The conditions utilized in the numerous hydrocarbon conversionembodiments of the present invention are in general those customarilyused in the art for the particular reaction, or combination ofreactions, that is to be effected. For instance, alkylaromatic andparaffin isomerization conditions include: a temperature of about 32° F.to about 1000° F. and preferably from about 75° to about 600° F.: apressure of atmospheric to about 100 atmospheres; a hydrogen tohydrocarbon mole ratio of about 0.5:1 to about 20:1, and an LHSV(calculated on the basis of equivalent liquid volume of the charge stockcontacted with the catalyst per hour divided by the volume of conversionzone containing catalyst) of about 0.2 hr.⁻ ¹ to 10 hr.⁻ ¹.Dehydrogenation conditions include: a temperature of about 700° to about1250° F., a pressure of about 0.1 to about 10 atmospheres, a liquidhourly space velocity of about 1 to 40 hr.⁻ ¹, and a hydrogen tohydrocarbon mole ratio of about 1:1 to 20:1. Likewise, typicallyhydrocracking conditions include: a pressure of about 500 psig. to about3000 psig., a temperature of about 400° F. to about 900° F., an LHSV ofabout 0.1 hr.⁻ ¹ to about 10 hr.⁻ ¹, and hydrogen circulation rates ofabout 1000 to 10,000 SCF per barrel of charge.

In the reforming embodiment of the present invention, the pressureutilized is selected from the range of about 0 psig. to about 1000psig., with the preferred pressure being about 50 psig. to about 600psig. Particularly good results are obtained at low or moderatepressure; namely, a pressure of about 100 to 450 psig. In fact, it is asingular advantage of the present invention that it allows stableoperation at lower pressure than have heretofore been successfullyutilized in so-called "continuous" reforming systems (i.e. reforming forperiods of about 15 to about 200 or more barrels of charge per pound ofcatalyst without regeneration) with all platinum monometallic catalyst.In other words, the acidic sulfur-free multimetallic catalyst of thepresent invention allows the operation of a continuous reforming systemto be conducted at lower pressure (i.e. 100 to about 350 psig.) forabout the same or better catalyst cycle life before regeneration as hasbeen heretofore realized with conventional monometallic catalysts athigher pressure (i.e. 400 to 600 psig.). On the other hand, theextraordinary activity and activity-stability characteristics of thecatalyst of the present invention enables reforming conditions conductedat pressures of 400 to 600 psig. to achieve substantially increasedcatalyst cycle life before regeneration.

The temperature required for reforming with the instant catalyst ismarkedly lower than that required for a similar reforming operationusing a high quality catalyst of the prior art. This significant anddesirable feature of the present invention is a consequence of theextraordinary activity of the acidic sulfur-free multimetallic catalystof the present invention for the octane-upgrading reactions that arepreferably induced in a typical reforming operation. Hence, the presentinvention requires a temperature in the range of from about 800° F. toabout 1100° F. and preferably about 900° F. to about 1050° F. As is wellknown to those skilled in the continuous reforming art, the initialselection of the temperature within this broad range is made primarilyas a function of the desired octane of the product reformate consideringthe characteristics of the charge stock and of the catalyst. Ordinarily,the temperature then is thereafter slowly increased during the run tocompensate for the inevitable deactivation that occurs to provide aconstant octane product. Therefore, it is a feature of the presentinvention that not only is the initial temperature requirementsubstantially lower but also the rate at which the temperature isincreased in order to maintain a constant octane product issubstantially lower for the catalyst of the present invention than foran equivalent operation with a high quality reforming catalyst which ismanufactured in exactly the same manner as the catalyst of the presentinvention except for the inclusion of the rhenium and nickel components.Moreover, for the catalyst of the present invention, the C₅ + yield lossfor a given temperature increase is substantially lower than for a highquality reforming catalyst of the prior art. The extraordinary activityof the instant catalyst can be utilized in a number of highly beneficialways to enable increased performance of a catalytic reforming processrelative to that obtained in a similar operation with a monometallic orbimetallic catalyst of the prior art, some of these are: (1) octanenumber of C₅ + product can be substantially increased withoutsacrificing catalyst run length, (2) the duration of the processoperation (i.e. catalyst run length or cycle life) before regenerationbecomes necessary can be significantly increased, (3) investment costscan be lowered without any sacrifice in cycle life by lowering recyclegas requirements thereby saving on capital cost for compressor capacityor by lowering initial catalyst loading requirements thereby saving oncost of catalyst and on capital cost of the reactors, (4) throughput canbe increased sharply at no sacrifice in catalyst cycle life ifsufficient heater capacity is available.

The reforming embodiment of the present invention also typicallyutilizes sufficient hydrogen to provide an amount of about 1 to about 20moles of hydrogen per mole of hydrocarbon entering the reforming zone,with excellent results being obtained when about 2 to about 6 moles ofhydrogen are used per mole of hydrocarbon. Likewise, the liquid hourlyspace velocity (LHSV) used in reforming is selected from the range ofabout 0.1 to about 10 hr.⁻ ¹, with a value in the range of about 1 toabout 5 hr.⁻ ¹ being preferred. In fact, it is a feature of the presentinvention that it allows operations to be conducted at higher LHSV thannormally can be stably achieved in a continuous reforming process with ahigh quality reforming catalyst of the prior art. This last feature isof immense economic significance because it allows a continuousreforming process to operate at the same throughput level with lesscatalyst inventory or at greatly increased throughput level with thesame catalyst inventory than that heretofore used with conventionalreforming catalysts at no sacrifice in catalyst life beforeregeneration.

The following working examples are given to illustrate further thepreparation of the acidic sulfur-free multimetallic catalytic compositeof the present invention and the use thereof in the conversion ofhydrocarbons. It is understood that the examples are intended to beillustrative rather than restrictive.

EXAMPLE I

A sulfur-free alumina carrier material comprising 1/16 inch spheres isprepared by: forming an aluminum hydroxyl chloride sol by dissovingsubstantially pure aluminum pellets in a hydrochloric acid solution,adding hexamethylenetetramine to the resulting sol, gelling theresulting solution by dropping it into an oil bath to form sphericalparticles of an aluminum hydrogel, aging and washing the resultingparticles, and finally drying and calcining the aged and washedparticles to form spherical particles of gamma-alumina containing about0.3 weight percent combined chloride. Additional details as to thismethod of preparing the preferred carrier material are given in theteachings of U.S. Pat. No. 2,620,314.

An aqueous acidic sulfur-free impregnation solution containingchloroplatinic acid, perrhenic acid, nickel chloride, and hydrogenchloride is then prepared. The alumina carrier material is thereafteradmixed with the impregnation solution. The amount of reagent containedin this impregnation solution is calculated to result in a finalcomposite containing, on an elemental basis, 0.375 wt. % platinum, 0.375wt. % rhenium, and 0.5 wt. % nickel. In order to insure uniformdispersion of the metallic components throughout the carrier material,the amount of hydrochloric acid used is about 3 wt. % of the aluminaparticles. This impregnation step is performed by adding the carriermaterial particles to the impregnation mixture with constant agitation.In addition, the volume of the solution is approximately the same as thevoid volume of the carrier material particles. The impregnation mixtureis maintained in contact with the carrier material particles for aperiod of about 1/2 to about 3 hours at a temperature of about 70° F.Thereafter, the temperature of the impregnation mixture is raised toabout 225° F. and the excess solution was evaporated in a period ofabout 1 hour. The resulting dried impregnated particles are thensubjected to an oxidation treatment in a sulfur-free dry air stream at atemperature of about 975° F. and a GHSV of about 500 hr.⁻ ¹ for about1/2 hour. This oxidation step is designed to convert substantially allof the metallic ingredients to the corresponding reducible oxide forms.The resulting oxidized spheres are subsequently contacted in ahalogen-treating step with a sulfur-free air stream containing H₂ O andHCl in a mole ratio of about 30:1 for about 2 hours at 975° F. and aGHSV of about 500 hr.⁻ ¹ in order to adjust the halogen content of thecatalyst particles to a value of about 1 wt. %. The halogen-treatedspheres are thereafter subjected to a second oxidation step with a drysulfur-free air stream at 975° F. and a GHSV of 500 hr.⁻ ¹ for anadditional period of about 1/2 hour.

The oxidized and halogen-treated catalyst particles are then subjectedto a dry prereduction treatment, designed to reduce substantially all ofthe platinum component to the elemental metallic state, by contactingthem for about 1 hour with a substantially hydrocarbon-free andsulfur-free hydrogen stream containing less than 5 vol. ppm. H₂ O at atemperature of about 1050° F., a pressure slightly above atmospheric,and a flow rate of the hydrogen stream through the catalyst particlescorresponding to a gas hourly space velocity of about 400 hr.⁻ ¹.

A sample of the resulting reduced catalyst particles is analyzed andfound to contain, on an elemental basis, about 0.375 wt. % platinum,about 0.375 wt. % rhenium, about 0.5 wt. % nickel, and about 1 wt. %chloride. This corresponds to an atomic ratio of rhenium to platinum of1.05:1 and to an atomic ratio of nickel to platinum of 4.4:1.

EXAMPLE II

A portion of the spherical acidic sulfur-free multimetallic catalystparticles produced by the method described in Example I is loaded into ascale model of a continuous, fixed bed reforming plant of conventionaldesign. In this plant a heavy Kuwait naphtha and hydrogen arecontinuously contacted at reforming conditions: a liquid hourly spacevelocity of 3.0 hr.⁻ ¹, a pressure of 300 psig., a hydrogen tohydrocarbon mole ratio of 8:1, and a temperature sufficient tocontinuously produce a C₅ + reformate of 100 F-1 clear. It is to benoted that these are exceptionally severe conditions.

The heavy Kuwait naphtha has an API gravity of 60° F. of 60.4, aninitial boiling point of 184° F., a 50% boiling point of 256° F., and anend boiling point of 360° F. In addition, it contains about 8 vol. %aromatics, 71 vol. % paraffins, 21 vol. % naphthenes, 0.5 weight partsper million sulfur, and 5 to 8 weight parts per million water. The F-1clear octane number of the raw stock is 40.0.

The fixed bed reforming plant is made up of a reactor containing theacidic, sulfur-free multimetallic catalyst, a hydrogen separation zone,a debutanizer column, and suitable heating, pumping, cooling, andcontrolling means. In this plant, a hydrogen recycle stream and thecharge stock are commingled and heated to the desired temperature. Theresultant mixture is then passed downflow into a reactor containing acatalyst as a fixed bed. An effluent stream is then withdrawn from thebottom of the reactor, cooled to about 55° F. and passed to a separatingzone wherein a hydrogen-rich and methane-rich gaseous phase separatesfrom a liquid hydrocarbon phase. A portion of the gaseous phase iscontinuously passed through a high surface sodium scrubber and theresulting water-free hydrogen-containing stream recycled to the reactorin order to supply hydrogen thereto, and the excess gaseous phase overthat needed for plant pressure is recovered as excess separator gas. Theliquid hydrocarbon phase from the hydrogen separating zone is withdrawntherefrom and passed to a debutanizer column of conventional designwherein light ends are taken overhead as debutanizer gas and a C₅ +reformate stream recovered as bottoms.

The test run is continued for a catalyst life of about 10 barrels ofcharge per pound of catalyst utilized, and it is determined that theactivity, selectivity, and stability characteristics of the presentmultimetallic catalyst are vastly superior to those observed in asimilar type test with a conventional all platinum commercial reformingcatalyst. More specifically, the results obtained from the subjectcatalyst are superior to the platinum metal-containing catalyst of theprior art in the area of initial temperature required to make octane,methane production, average C₅ + yield at octane, average rate oftemperature increase necessary to maintain octane and C₅ + yield declinerate.

It is intended to cover by the following claims, all changes andmodifications of the above disclosure of the present invention whichwould be self-evident to a man of ordinary skill in the catalystformulation art or the hydrocarbon conversion art.

I claim as my invention:
 1. A process for catalytically reforming agasoline fraction which comprises contacting said fraction at reformingconditions which include a temperature of about 800° to about 1100°F anda pressure of about 0 to about 1000 psig, with an acidic sulfur-freecatalytic composite comprising a porous carrier material containing, onan elemental basis, about 0.01 to about 2 wt. % platinum group metal,about 0.1 to about 5 wt. % nickel, about 0.01 to about 2 wt. % rhenium,and about 0.1 to about 3.5 wt. % halogen, wherein the platinum groupmetal, nickel, and rhenium are uniformly dispersed throughout the porouscarrier material, wherein substantially all of the platinum group metalis present in the elemental metallic state, and wherein substantiallyall of the nickel and rhenium are present in the elemental metallicstate or in a state which is reducible to the elemental metallic stateunder hydrocarbon conversion conditions or in a mixture of these states.2. A process as defined in claim 1 wherein the platinum group metal isplatinum.
 3. A process as defined in claim 1 wherein the platinum groupmetal is iridium.
 4. A process as defined in claim 1 wherein theplatinum group metal is rhodium.
 5. A process as defined in claim 1wherein the platinum group metal is palladium.
 6. A process as definedin claim 1 wherein the porous carrier material is a refractory inorganicoxide.
 7. A process as defined in claim 6 wherein the refractoryinorganic oxide is alumina.
 8. A process as defined in claim 1 whereinthe halogen is combined chloride.
 9. A process as defined in claim 1wherein the atomic ratio of rhenium to platinum group metal contained inthe composite is about 0.05:1 to about 10:1.
 10. A process as defined inclaim 1 wherein the atomic ratio of nickel to platinum group metalcontained in the composite is about 0.2:1 to about 66:1.
 11. A processas defined in claim 1 wherein substantially all of the nickel andrhenium contained in the composite are present in the elemental metalicstate.
 12. A process as defined in claim 1 wherein the compositecontains about 0.05 to about 1 wt. % platinum, about 0.25 to about 2.5wt. % nickel, about 0.05 to about 1 wt. % rhenium, and about 0.5 toabout 1.5 wt. % halogen.
 13. A process as defined in claim 1 wherein thecontacting of the hydrocarbon with the catalytic composite is performedin the presence of hydrogen.
 14. A process as defined in claim 1 whereinthe type of hydrocarbon conversion is catalytic reforming of a gasolinefraction to produce a high octane reformate, wherein the hydrocarbon iscontained in the gasoline fraction, wherein the contacting is performedin the presence of hydrogen, and wherein the hydrocarbon conversionconditions are reforming conditions.
 15. A process as defined in claim14 wherein the reforming conditions include a temperature of about 800°to about 1100°F., a pressure of about 0 to about 1000 psig., a liquidhourly space velocity of about 0.1 to about 10 hr.⁻ ¹, and a mole ratioof hydrogen to hydrocarbon of about 1:1 to about 20:1.
 16. A process asdefined in claim 14 wherein the contacting is performed in asubstantially water-free environment.
 17. A process as defined in claim14 wherein the reforming conditions include a pressure of about 100 toabout 450 psig.
 18. A process as defined in claim 14 wherein thecontacting is performed in a substantially sulfur-free environment. 19.A process as defined in claim 12 wherein the type of hydrocarbonconversion is catalytic reforming of a gasoline fraction to produce ahigh octane reformate, wherein the hydrocarbon is contained in thegasoline fraction, wherein the contacting is performed in the presenceof hydrogen and wherein the hydrocarbon conversion conditions arereforming conditions.